Saturday, October 2, 2010

Potatoes and Human Health, Part III

Potato-eating Cultures: the Quechua

The potato is thought to have originated in what is now Peru, on the shores of lake Titicaca. Native Peruvians such as the Quechua have been highly dependent on the potato for thousands of years. A 1964 study of the Quechua inhabitants of Nuñoa showed that they obtained 74% of their calories from potatoes (fresh and chuños), 10% from grains, 10% from Chenopodia (quinoa and cañihua), and 4% from animal foods. Total energy intake was 3,170 calories per day (1).

In 2001, a medical study of rural Quechua men reported an average body fat percentage of 16.4% (2). The mean age of the volunteers was 38. Body fat did increase slowly with age in this population, and by age 65 it was predicted to be about 20% on average. That's below the threshold of overweight, so I conclude that most men in this population are fairly lean, although there were a few overweight individuals.

In 2004, a study in rural Quechua women reported a body fat percentage of 31.2% in volunteers with a mean age of 35 (3). Body fat percentage was higher in a group of Quechua immigrants to the Peruvian capital of Lima. Among rural women, average fasting insulin was 6.8 uIU/mL, and fasting glucose was 68.4 mg/dL, which together suggest good insulin sensitivity and glucose control (4). Insulin and glucose were considerably lower in the rural group than the urban group. Blood pressure was low in both groups. Overall, this suggests that overweight is common among Quechua women.

Rural Quechua are characteristically short, with the average adult man standing no more than 5' 2" (2). One might be tempted to speculate that this reflects stunting due to a deficient diet. However, given the fact that nearly all non-industrial populations, including contemporary hunter-gatherers, are short by modern standards, I'm not convinced the Quechua are abnormal. A more likely explanation is that industrial foods cause excessive tissue growth in modern populations, perhaps by promoting overeating and excessive insulin and IGF-1 production, which are growth factors. I first encountered this hypothesis in Dr. Staffan Lindeberg's book Food and Western Disease.

I don't consider the Quechua diet to be optimal, but it does seem to support a reasonable level of metabolic health. Rural Quechua men subsisting on potatoes are relatively lean, while women are often overweight, though less overweight than urban Quechua who eat fewer potatoes. Unfortunately, I don't have more detailed data on other aspects of their health, such as gastrointestinal health.
Potato-eating Cultures: the Aymara

The Aymara are another potato-dependent people of the Andes, who span Peru, Bolivia and Chile. The first paper I'll discuss is titled "Low Prevalence of Type II Diabetes Despite a High Body Mass Index in the Aymara Natives From Chile", by Dr. Jose Luis Santos and colleagues (5). In the paper, they show that the prevalence of diabetes in this population was 1.5%, and the prevalence of pre-diabetes was 3.6%. The prevalence of both remained low even in the elderly. Here's a comparison of those numbers with figures from the modern United States (6):

That's quite a difference! The prevalence of diabetes in this population is low, but not as low as in some cultures such as the Kitavans (7, 8).

Now to discuss the "high body mass index" referenced in the title of the paper. The body mass index (BMI) is the relation between height and weight, and often, but not always, reflects fatness. The average BMI of this population was 24.9, which is very close to the cutoff between normal and overweight (25).

Investigators were surprised to find such a low prevalence of diabetes in this population, despite their apparent high prevalence of overweight. Yet if you've seen pictures of rural native South Americans, you may have noticed they're often built short and thick, with wide hips and big barrel chests. Could this be confounding the relationship between BMI and body fatness? To answer that question, I found another paper that estimated Aymara body fat using skinfold measurements (9). That study reported that both men and women remained relatively lean throughout life (ages 4-65), with only two of 23 subjects classified as overweight on the basis of body fat percentage, and none classified as obese.

Back to the first paper. In this Aymara group, blood pressure was on the high side. Serum cholesterol was also a bit high for a traditionally-living population, but still lower than most modern groups (~188 mg/dL). I find it very interesting that the cholesterol level in this population that eats virtually no fat was the same as on Tokelau, where nearly half of calories come from highly saturated coconut fat (10, 11). Fasting insulin is also on the high side in the Aymara, which is also interesting given their good glucose tolerance and low prevalence of diabetes. This could be related to differences in the measurement assay rather than a true difference in fasting insulin, since these assays were often not standardized between studies.

Together, this shows that a lifetime of high-carbohydrate, high-glycemic food does not necessarily lead to overweight or metabolic problems in the context of a traditional diet and lifestyle.
Potato-eating Cultures: the Irish

Potatoes were introduced to Ireland in the 17th century. They were well suited to the cool, temperate climate, and more productive than any other crop. By the early 18th century, potatoes were the main source of calories, particularly for the poor who ate practically nothing else. In 1839, the average Irish laborer obtained 87% of his calories from potatoes (12). In 1845, the potato blight Phytophthora infestans struck, decimating potato plantations nationwide and creating the Great Famine.

There isn't much reliable information on the health status of the Irish prior to the famine, besides reports of vitamin A deficiency symptoms (13) due to the fact that neither of the primary articles of diet, potatoes and buttermilk, provide significant vitamin A. However, the Irish at the time had a very high fertility rate, and anecdotal reports described them as healthy and attractive (14):

As far as fecundity is concerned, the high nutritional value of the potato diet might have played a significant role, but little supportive evidence has been presented so far... What is known is that the Irish in general and Irish women in particular were widely described as healthy and good-looking. Adam Smith's famous remark that potatoes were "peculiarly suitable to the health of the human constitution" can be complemented with numerous observations from other contemporary observers to the same effect.

Controlled Feeding Studies

Starting nearly a century ago, a few researchers decided to feed volunteers potato-only diets to achieve various research objectives. The first such experiment was carried out by a Dr. M. Hindhede and published in 1913 (described in 15). Hindhede's goal was to explore the lower limit of the human protein requirement and the biological quality of potato protein. He fed three healthy adult men almost nothing but potatoes and margarine for 309 days (margarine was not made from hydrogenated seed oils at the time), all while making them do progressively more demanding physical labor. They apparently remained in good physical condition. Here's a description of one of his volunteers, a Mr. Madsen, from another book (described in 16; thanks to Matt Metzgar):

In order to test whether it was possible to perform heavy work on a strict potato diet, Mr. Madsen took a place as a farm laborer... His physical condition was excellent. In his book, Dr. Hindhede shows a photograph of Mr. Madsen taken on December 21st, 1912, after he had lived for almost a year entirely on potatoes. This photograph shows a strong, solid, athletic-looking figure, all of whose muscles are well-developed, and without excess fat. ...Hindhede had him examined by five physicians, including a diagnostician, a specialist in gastric and intestinal diseases, an X-ray specialist, and a blood specialist. They all pronounced him to be in a state of perfect health.

Dr. Hindhede discovered that potato protein is high quality, providing all essential amino acids and high digestibility. Potato protein alone is sufficient to sustain an athletic man (although that doesn't make it optimal). A subsequent potato feeding study published in 1927 confirmed this finding (17). Two volunteers, a man and a woman, ate almost nothing but potatoes with a bit of lard and butter for 5.5 months. The man was an athlete but the woman was sedentary. Body weight and nitrogen balance (reflecting protein gain/loss from the body) remained constant throughout the experiment, indicating that their muscles were not atrophying at any appreciable rate, and they were probably not putting on fat. The investigators remarked:

The digestion was excellent throughout the experiment and both subjects felt very well. They did not tire of the uniform potato diet and there was no craving for change.

In one of his Paleo Diet newsletters titled "Consumption of Nightshade Plants (Part 1)", Dr. Loren Cordain referenced two feeding studies showing that potatoes increase the serum level of the inflammatory cytokine interleukin-6 (22, 23). However, one study was not designed to determine the specific role of potato in the change (two dietary factors were altered simultaneously), and the other used potato chips as the source of potato. So I don't find these studies particularly relevant to the question at hand.

Just yesterday, Chris Voigt of the Washington State Potato Commission embarked on his own n=1 potato feeding experiment as a way to promote Washington state potatoes. He'll be eating nothing but potatoes and a little fat for two months, and getting a full physical at the end. Check out his website for more information and updates (18). Mr. Voigt has graciously agreed to a written interview with Whole Health Source at the end of his experiment. He pointed out to me that the Russet Burbank potato, the most popular variety in the United States, is over 135 years old. Stay tuned for more interesting facts from Mr. Voigt in early December.

Observational Studies

With the recent interest in the health effects of the glycemic index, a few studies have examined the association between potatoes and health in various populations. The results are all over the place, with some showing positive associations with health, and others showing negative associations (19, 20, 21). As a whole, I find these studies difficult to interpret and not very helpful.

Anecdotes

Some people feel good when they eat potatoes. Others find that potatoes and other members of the nightshade family give them digestive problems, exacerbate their arthritis, or cause fat gain. I haven't encountered any scientific research to substantiate claims that nightshades aggravate arthritis or other inflammatory conditions. However, that doesn't necessarily mean there aren't individuals who are sensitive. If potatoes don't agree with you, by all means avoid them.

The Bottom Line

You made it to the end! Give yourself a pat on the back. You deserve it.

In my opinion, the scientific literature as a whole, including animal and human studies, suggests rather consistently that potatoes can be a healthy part of a varied diet for most people, and they probably do not generally promote digestive problems, fat gain, or metabolic dysfunction. Nevertheless, I wouldn't recommend eating nothing but potatoes for any length of time. If you do choose to eat potatoes, follow these simple guidelines:

Don't eat potatoes that are green, sprouting, blemished, or damaged

Store them in a cool, dark place. They don't need to be refrigerated but it will extend their life

I've enjoyed this whole series. Potatoes don't seem to agree with me, but I'm glad they're a good food for most people. As always (and I say that advisedly), great work!

One thing I really like about your blog, aside from its breadth, depth, good writing, good research, and good analysis, is that you aren't grinding any particular axe when it comes to diet (albeit within the context of whole and traditional), so you are willing to explore a lot of possibilities about what contributes to good health vs. disease. It makes for reading that is both interesting and useful.

1) You said "non-industrial populations, including contemporary hunter-gatherers, are short by modern standards." I thought the receieved wisdom was that people were tall until they started eating grain.

Great work, Stephan, thanks a lot. Accidently I started with potatoes and yams 4 weeks ago. After nearly 1 year keto/VLC. First with caution one by one and now I have very often huge potatoe meals + lots of fat + fish. BG before around 70 post prandial 85. I have more energy, gain muscles again, sleep better, improved my lowish fT3 and finally lost some stubborn pounds. Amazingly with more calories than prior. IMHO natural eating is not low carb by all means. There is no dogma. If you tolerate it so give it a try. Greetings.

Great work, Stephan, thanks a lot. Accidently I started with potatoes and yams 4 weeks ago. After nearly 1 year keto/VLC. First with caution one by one and now I have very often huge potatoe meals + lots of fat + fish. BG before around 70 post prandial 85. I have more energy, gain muscles again, sleep better, improved my lowish fT3 and finally lost some stubborn pounds. Amazingly with more calories than prior. IMHO natural eating is not low carb by all means. There is no dogma. If you tolerate it so give it a try. Greetings.

Glad to hear the potato being exonerated! I can't believe how many people believe the potato is flat out unhealthy. They lump it in with other "white" foods like refined sugar and flour. What a shame. Like you said, potatoes might not be the ideal food for everyone, but they can certainly be part of a healthy diet for many people.

Very interesting. Dr Kwasniewski (sp?) is a fan of potatoes. I've adopted his ideas when I've been struggling financially. $2 worth of potatoes goes a long way. I'd have taters a few times a week. I find a small potato cooked in animal fat to be a very satisfying side dish. I get no cravings, I stay full for a long time, and I get no symptoms of wonky blood sugar (though I wish I had a glucometer.)

I rarely comment, but thanks for a very good blog. I second Helen's comments.

thanks for the post, Stephan! I fully enjoy your work because you always approach food with the oldest traditional dietary records you can find, and back your words up with scientific studies. =)

I don't know if you have heard of the book "food energetics" by Steve Gagne. I just received my copy yesterday and couldn't get my eyes off the book the entire time. This is an extraordinary book also approaches food from the traditional, sometimes ancient knowledges about foods, their characters, and qualities that we have long forgotten. It is beautifully versed, with delightful humors, and love. I highly highly recommend it..

anyways, back to potatoes.I agree that potatoes can be eaten as a part of a healthy diet, but I can't agree that people should eat it often.. nightshades in general should be eaten in limited amount in my opinion..

I wanted to point out about the history of potatoes eaten in Europe, that the "Food Energetic" and my earlier readings in "food and agarian orders in the world economy" coincide with the statement that it wasn't a natural dietary selection that the irish people started to eat potatoes, and that although they were introduced to the european people in the 17th century, it wasn't until 19th centry did they really became "traditional".

I'll write you an eamil with better quotes later. it is fascinating. =)enough rambling, I thank you for your wonderful post, cheers.

This is a very interesting series. Thank you for putting it together. We now have more evidence that a diet consisting of a wide variety of foods as close to their natural state is best (something my grandmother always said). But most of all my beloved potato has been given a clean bill of health.

Yes, my code for foods like this is FDV (Fat Delivery Vehicle). Another is EDV (Egg Delivery Vehicle). Sort of a Mary Poppins thing except without the spoonful of sucrose/fructose.

Anyone have any thoughts on TJ's new cassava chips as an occasional FVD?

Labeled as GF. Don't have the package in front of me, but I think I remember the ingredients indicate they are cooked in palm oil, though they also had a small amount of cane sugar and something that spices them up a bit (sorry, faulty memory), s the flavor is slightly sweet-hot. More flavored than a plain potato chip, but not nearly as over-flavored as a Dorito-type chip. Relative short list of ingredients, if I remember correctly, too (unlike Dorito-types).

Enjoying the post series and reader comments about potatoes. I still limit my consumption to a few rare bites, because my glucose meter isn't happy with more than that. Sigh. When I do prepare taters, it's organic only (from our CSA box). Potatoes are a heavily treated crop.

quoting from the book I'm reading, "poisonous alkaloids called solanines appear as a green color on potato skins, particularly when they are exposed to light. The solanie level of most potatoes is about 90 parts per million (ppm), which is about one quater of the danger level determined by researchers."

You have enso - sunyata - in your new logo! I love it. DId you design it yourself? One of the reasons I have been blogging less lately is I have been distracted by several non-nutritional topics. A book I am reading right now is "Buddha's Brain" by Rick Hanson. You would probably enjoy it, as it is written by a Theravada practitioner who references real neuroscience.

I loved the potato series. I am firmly in your camp on the acceptability of starch for the non-metabolically damaged. The historical record supports it.

Starch is not a neolithic agent of disease!

PS - I had hash browns fried in coconut with pastured eggs and bacon for breakfast

I notice the phrase "potato-only diet" is used to refer to a diet of potatoes and fat. I wonder how many people in the mainstream hear "you can be healthy on a potato-only diet" and think it really means potatoes only, thus reinforcing their low-fat beliefs.

Potatoes from a box? That stuff is gross-doesn't even taste like potato and probably has a lot of not potato ingredients.

As far as super starchy diets, I am still not convinced they are as healthy as eating more meat and fish, but in some places, they need the tubers for survival. I'd bet they'd eat steak instead if it was available though!

Also, I suspect starches can cause more probs for those many in industrialized countries who are more sedentary and already have damaged metabolisms.

Another interesting thing about potatoes is that it is super satiating.

http://www.ncbi.nlm.nih.gov/pubmed/7498104

The boiled potato has the highest satiety index. I am sure that with fat the satiety index will be slightly lower, but nevertheless a great vehicle to lose fat. Health effects that are accessible to cultural vegetarians as well.

I loved this post. You wrote, "I don't consider the Quechua diet to be optimal,...". So which diets do you consider to be optimal? Do you have some favorites from around the world, current and/or historical?

Yes, that's true. It could be due to genetic selection for smaller body size, or differences in the diets of ancient vs. modern HGs.

Potato peels are nutritious but contain toxins.

Hi portland_allan,

Cooking has virtually no impact on glycoalkaloids.

Hi Hans,

Basically, I wouldn't recommend eating potatoes exclusively on principle, just as I wouldn't recommend eating any other food exclusively. Better to keep the diet varied to minimize the intake of specific toxins and diversify the micronutrient intake.

Glad you noticed! I did design the logo myself. Thanks for the book recommendation.

Hi Lisa,

I don't know if any culture truly has an optimal diet, if such a thing even exists, but I think the Kitavan diet is probably superior to the Quechua/Aymara diet. Kitavans get more animal foods and more fat. Hunter-gatherers in the Pacific Northwest had a very good diet as well: lots of fish, shellfish, land mammals, tubers and various gathered plant foods.

If I were to design an "optimal diet", it would be based mostly on starchy tubers (multiple kinds), pastured meats including organs, wild-caught seafood, and vegetables. It might also contain a smaller amount of fermented non-gluten grains, beans, fruit, eggs and dairy. But realistically, it would depend on the individual.

First time poster here, but I've been lurking at your site for some time now. Keep up the great work.

I'd like to share a precautionary note on what appears to be strong affirmations of the potato's safety based on very limited data. I have the same reservations about sweeping safety statements about sweet potatoes (or carbohydrates in general) based on Kitavan studies. Both the Nunos and the Kitavan folks provide useful information in our pursuit for "perfect" health, but I'm not sure how much emphasis should be placed on information gathered from homogeneous populations eating such limited homogeneous diets. It could very well be that potatoes (and the variety eaten by the folks from Kitivan--a different species altogether) are inflammatory (non-optimal/harmful, take your pick) on our bodies but that other factors in these homogeneous diets are protective of these harmful effects. For example, the Kitavans consistently ingest both fish and coconuts--both of which could provide anti-inflammatory protection against the carbs inflammatory effects. Plausible, I believe—definitely worth keeping in mind.

Having said that, I can’t immediately see from the 1964 study what would provide such protection in the folks of Nunos. Their diet appears highly inflammatory, with very few anti-inflammatory components. It doesn’t mean there are not present, but the 1964 study provides very little to suggest that there was much of an anti-inflammatory component. And it’s quite difficult to estimate the robustness of the 1964 study as it hasn’t been reproduced and several later studies are in partial conflict with it—especially as to daily caloric intake (Pawson et al 2010, Pawson et al 2001, de Meer et al 1993, Leonard et al 1989, Leatherman et al 1995, Leonard 1997). From all these studies, it seems the children of Nunos were never all that healthy to begin with and that this particular diet may account for the low stature of these people. The information is difficult to interpret because of the many variables and cofounders, the drastic cultural changes forced on these people because of political forces over the years, the development of socioeconomic classes, the change in diet, etc. One trend I did notice is that over the years the more affluent—who had access to more Western foods—did not necessarily become more “unhealthy” or develop the diseases of civilization (these might become more apparent given a few more years, though). What is also interesting is that the children of the affluent are bigger in stature than their less affluent counterparts. There’s mention in one of the studies that the affluent consume four times the amount of fats as the less affluent, but it’s not clear whether fat intake comes from animal products (which are usually sold outside the locale) or from plant oils. So, personally, I’m not ready to give the potato (or carbohydrates) a clean bill of “optimal” health yet. But I find it very informative and useful. BTW, I do include small portions of potatoes to my meals, so I'm not anti-potato.

Sorry for the long post. I thought it might be useful to you and your readership to share my prejudice of homogeneous sampling. Or not. ;-)

First time poster here, but I've been lurking at your site for some time now. Keep up the great work.

I'd like to share a precautionary note on what appears to be strong affirmations of the potato's safety based on very limited data. I have the same reservations about sweeping safety statements about sweet potatoes (or carbohydrates in general) based on Kitavan studies. Both the Nunos and the Kitavan folks provide useful information in our pursuit for "perfect" health, but I'm not sure how much emphasis should be placed on information gathered from homogeneous populations eating such limited homogeneous diets. It could very well be that potatoes (and the variety eaten by the folks from Kitivan--a different species altogether) are inflammatory (non-optimal/harmful, take your pick) on our bodies but that other factors in these homogeneous diets are protective of these harmful effects. For example, the Kitavans consistently ingest both fish and coconuts--both of which could provide anti-inflammatory protection against the carbs inflammatory effects. Plausible, I believe—definitely worth keeping in mind.

Having said that, I can’t immediately see from the 1964 study what would provide such protection in the folks of Nunos. Their diet appears highly inflammatory, with very few anti-inflammatory components. It doesn’t mean there are not present, but the 1964 study provides very little to suggest that there was much of an anti-inflammatory component. And it’s quite difficult to estimate the robustness of the 1964 study as it hasn’t been reproduced and several later studies are in partial conflict with it—especially as to daily caloric intake (Pawson et al 2010, Pawson et al 2001, de Meer et al 1993, Leonard et al 1989, Leatherman et al 1995, Leonard 1997). From all these studies, it seems the children of Nunos were never all that healthy to begin with and that this particular diet may account for the low stature of these people. The information is difficult to interpret because of the many variables and cofounders, the drastic cultural changes forced on these people because of political forces over the years, the development of socioeconomic classes, the change in diet, etc. One trend I did notice is that over the years the more affluent—who had access to more Western foods—did not necessarily become more “unhealthy” or develop the diseases of civilization (these might become more apparent given a few more years, though). What is also interesting is that the children of the affluent are bigger in stature than their less affluent counterparts. There’s mention in one of the studies that the affluent consume four times the amount of fats as the less affluent, but it’s not clear whether fat intake comes from animal products (which are usually sold outside the locale) or from plant oils. So, personally, I’m not ready to give the potato (or carbohydrates) a clean bill of “optimal” health yet. But I find it very informative and useful. BTW, I do include small portions of potatoes to my meals, so I'm not anti-potato.

Sorry for the long post. I thought it might be useful to you and your readership to share my prejudice of homogeneous sampling. Or not. ;-)

Hello. You helped me on a web board about a year ago regarding the dangers of using the Friedewald formula for people on low carb diets.

For what it's worth, I started showing the symptoms of metabolic syndrome in my mid 40s during a 2-3 year period when I was eating about half a potato every day; prior to that my carbohydrate intake was mostly wheat. I'm also one of those that gets arthritis from nightshades - possibly more a tomato issue than a potato issue for me - based on an elimination diet. You can add that to your store of anecdotal data.

My main point, however, is that safety of potatoes in a traditional diet does not equate to safety for affluent westerners. I expect if you looked at Chinese data, for example, you'd find just as positive results for diets with a lot of rice, or even with a lot of wheat; certainly few of them get fat. People who can't afford more calories than they need to burn off don't tend to get fat, no matter what they eat.

Really enjoyed this series, thank you yet again! I sort of felt Cordain was being overly "alarmistic" again... It's good to feel safe about having potatoes now and then.

Now, I think a lot of readers other than myself are pondering what I'm pondering. You seem to have a bit of a preference for carbohydrates (NTTAWWT). It may just be your niche in the paleo blogging scene (your way of having a unique voice), or maybe there's something else behind it, some more esoteric knowledge? Here's the question:

- Are there reasons to believe a low-carber's health would improve by upping the carbs (from safe sources) from, say, 50-80 g/d to, say, 150 or even beyond?

- Also, do you disagree with the paleo notion that people - especially us of northern European descent - haven't *optimally* evolved to deal with high glycemic loads?

The ethnographic data seems to suggest many people in the southern hemisphere don't suffer overtly, according to certain parametres, from high GL eating. That's valuable information: we can use that to target the real offenders more specifically (sugat, wheat, vegetable oils...). But exactly *how* valuable is that information to us who are trying to have optimal health in an affluent context?

I'm quite sure these are baffling other readers as well, so I'd LOVE even a quick response. Thanks so much, keep up the great work!

I think that most people are genetically adapted to a significant amount of carbohydrate. Throughout the world, high-carb cultures are healthy as long as they don't eat industrial food. High-fat cultures are healthy as well, but there are not nearly as many examples of them.

I think that most people have an evolutionary past that hasn't been particularly low-carb for hundreds of thousands of years. Our African hunter-gatherer ancestors probably ate a substantial amount of starchy root vegetables (amount uncertain, but certainly varied by season and other factors). Muskiet and Cordain just published a paper estimating that our African HG ancestors ate about 40% of energy as carb.

Then, there was agriculture. Descendants of agricultural populations clearly have genetic adaptations to agricultural food sources, but the question is how completely are we adapted? No one knows the answer to that, but it's neither "not at all" nor "completely".

If I understand correctly, European HGs didn't really adopt agriculture. They were genetically replaced by agricultural and pastoralist populations. So the archaeological sites showing carnivorous European humans probably don't represent our ancestors.

I don't know what amount of carbohydrate is optimal, but it likely depends on the individual. I think very high carb (70% +) is probably not optimal for most people, and very low carb (10% or less) probably isn't optimal for most either. There seem to be people in affluent nations who genuinely benefit from carb restriction, I don't dispute that. But I doubt carbs per se caused the problem to begin with, as you don't see those types of metabolic issues in high-carb traditional cultures.

I think many questions remain, but generally I don't see much of a role for starch per se in the diseases of civilization.

Having spent some time on the Andean Ridge, I'm not convinced that the Quechua and Aymara are good health models... they have an extremely short life expectancy (males <50 years), but it's quite difficult (impossible, maybe) to tease out the effects of their diet from confounding factors (high-risk employment, inadequate health care).

I'd read about the potato flack's anticipated potato diet. I'll be watching his site -- and yours -- with interest.

Congratulations Stephan, though I read many blogs you are the first to convince me to sign up for some bullshit username to leave an identity. The fact that you don't have anonymous commenting pisses off many people and probably loses you valued insight into many of your posts. However, I have a worry serious enough to break my fuck you stance against Google's increasing attempt to monitor people's activities online.

I have been following a low carb paleo diet with resounding success for some months now. My negotiation skills aren't great (as you can no doubt) tell and I've had little success in persuading my family to cut the CW crap.

However, my one and only sister is a vegetarian. Her main food consists of potatoes and bread. I can not see anyway to get her to eat meat. She looks healthy enough though I suspect her mood swings are a reaction to all the carbs and I'm worried she might be pre-diabetic.

Your post on potatoes reassure me somewhat, but my real question is, what is the healthiest way to structure a diet around potatoes? What supplements does she need? What foods does she need most to make up for a lack of EFAs and protein not provided by potatoes?Even small things like ditching the margarine for butter would help.Any advice would be appreciated?

"If I were to design an "optimal diet", it would be based mostly on starchy tubers (multiple kinds), pastured meats including organs, wild-caught seafood, and vegetables. It might also contain a smaller amount of fermented non-gluten grains, beans, fruit, eggs and dairy. But realistically, it would depend on the individual."

This is a great piece. Perhaps you could put something like this on a separate page, along with some of your other diet principles? Your own sort of 'get started' page.

Hi- Great series! I was told that most of the nutrients in potatoes reside just underneath the skin, so peeling them removes both the fiber in the skin and the nutrients underneath. I recently observed my husband's German mother making her traditional potato salad by boiling small red potatoes then peeling them with a pairing knife. This is a much more tedious process than peeling them raw but doesn't remove any of the the flesh beneath the skin. If it is true that the nutrients are concentrated directly under the skin, then this preparation method would be superior and perhaps why the Germans adopted it. My mother-in-law didn't know why she did it that way, but stuck to it even when we tried to convince her that peeling the potatoes raw would be much more efficient! BTW, I have also read the recommendation, I think from the WAPF folks, to peel some of the potatoes in a batch but not all to get some of the fiber in the skin but decrease the toxins.

Gary Taubes has made the point that all these "healthy" high carb diets are found in subsistence cultures where there is no real opportunity or motivation to overeat.

A 3000KCal diet is almost 4kg of boiled potatoes. There is no real risk of unwittingly overeating on such a diet. In fact you would probably have to really force yourself to eat enough just to maintain weight.

The Irish traditionally ate their potatoes half-cooked. The people of the Andes do likewise. This mean that a lot of the starch isn't gelatinised.

Sweet potatoes contain large amounts of retrograde starches which revert to a non-gelatinised state as they cool.

So it is likely that the Kitivans, Irish and Peruvians aren't really getting a large change in blood glucose despite a high carbohydrate diet. They would also be producing a lot of volatile fatty acids (and flatus) from gut fermentations.

Agriculture arrived very late in northern Europe. Grains were very rarely eaten in Iceland before the late 1800s. Weston Price noted in the 1920s that a little girl in the Outer Hebrides had never seen an apple before.

Northern Europe has been continuously populated for over 40,000 years. In fact history shows us that northern Europeans were the ones doing the displacing.

Vikings had settlements as far south as Sicily and as far east as Turkey. Rome was overrun and defeated by Scandinavian "barbarians" who decided to stay. The entire white male population of England is of Scandinavian origin.

"Starch consumption is a prominent characteristic of agricultural societies and hunter-gatherers in arid environments. In contrast, rainforest and circum-arctic hunter-gatherers and some pastoralists consume much less starch1, 2, 3. This behavioral variation raises the possibility that different selective pressures have acted on amylase, the enzyme responsible for starch hydrolysis4. We found that copy number of the salivary amylase gene (AMY1) is correlated positively with salivary amylase protein level and that individuals from populations with high-starch diets have, on average, more AMY1 copies than those with traditionally low-starch diets. Comparisons with other loci in a subset of these populations suggest that the extent of AMY1 copy number differentiation is highly unusual. This example of positive selection on a copy number–variable gene is, to our knowledge, one of the first discovered in the human genome. Higher AMY1 copy numbers and protein levels probably improve the digestion of starchy foods and may buffer against the fitness-reducing effects of intestinal disease."

This suggests that tolerance to dietary starches is highly variable and genetically based.

The Kitivans and Andeans are probably rare exceptions that can tolerate very high starch diets. This is mostly likely due to thousands of years of very powerful selection to a tuber based diet.

From everything I've read primarily carnivorous societies such as Inuits and Australian aborigines have an extremely poor tolerance of starchy foods.

I haven't had a chance to review the paper (design, methodology, etc.). It would be interesting to see what role exercise plays in regards to keep blood sugars low. The study apparently separates groups into "urban" and "suburban" but the post doesn't go into detail as to sedentary/non-sedentary habits of these two groups (have to assume that the suburban group is fairly non-sedentary).

It is certainly possible that highly active individuals, as a group, might be exhibit fairly low fasting blood glucose levels regardless of the type of diet.

In other words, the results might be the same if you substituted high protein, vitamin enriched white bread (or some other high glycemic item) for potatoes--assuming all other things are equal.

I apologize if this question is answered in the comments (or somewhere in the blog post), and I missed it.

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I'm an obesity researcher, neurobiologist, and author. In addition to my research, I enjoy synthesizing and communicating science for a general audience. I have a BS in biochemistry (University of Virginia) and a PhD in neurobiology (University of Washington).
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